Remove machine_cool_zone_length

We might introduce it again once we can sync this data from the firmware.

Contributes to issue CURA-2795.

resources/definitions/fdmprinter.def.json

@@ -235,22 +235,12 @@
                     "settable_per_extruder": true,
                     "settable_per_meshgroup": false
                 },
-                "machine_cool_zone_length":
-                {
-                    "label": "Cool Zone Length",
-                    "description": "The length of the piece that dissipates heat from the hot end to shield heat-sensitive equipment.",
-                    "default_value": 0,
-                    "type": "float",
-                    "settable_per_mesh": false,
-                    "settable_per_extruder": true,
-                    "settable_per_meshgroup": false
-                },
                 "machine_filament_park_distance":
                 {
                     "label": "Filament Park Distance",
                     "description": "The distance from the tip of the nozzle where to park the filament when an extruder is no longer used.",
                     "default_value": 16,
-                    "value": "machine_heat_zone_length + machine_cool_zone_length",
+                    "value": "machine_heat_zone_length",
                     "type": "float",
                     "settable_per_mesh": false,
                     "settable_per_extruder": true,

resources/definitions/ultimaker3.def.json

@@ -38,7 +38,7 @@
         "machine_depth": { "default_value": 215 },
         "machine_height": { "default_value": 200 },
         "machine_heated_bed": { "default_value": true },
-        "machine_cool_zone_length": { "default_value": 26.5 },
+        "machine_filament_park_distance": { "value": "machine_heat_zone_length + 26.5" },
         "machine_nozzle_heat_up_speed": { "default_value": 1.4 },
         "machine_nozzle_cool_down_speed": { "default_value": 0.8 },
         "machine_head_with_fans_polygon":